What is Essential Mineral Elements?
An essential element is the one that has a specific structural or physiological role and without which plant cannot complete its life cycle.
Different criteria for knowing the essentiality of elements are as follows:
- The element must be absolutely essential for supporting the normal growth and reproduction of plants.
- The element must be directly involved in the nutrition of plants.it either a component of an organic molecule or participates in a biochemical reaction.
- The requirement of the particular element must be specific. It cannot be replaced by any other element.
Almost 17 elements have been found to be essential. They are C, H, O, N, P, K, S, Mg, Ca, Fe, B, Mn, Cu, Mo, CI, and Ni.
- Macroelements are those essential elements that are present in easily detectable quantities1-10mg/gm of dry matter. They are nine in number –C, H, O, N, P, K, S, Mg and Ca.
- Microelements are those essential elements that are required by plants in small amounts (less than 0.1 mg/gm of dry matter). Microelements are mostly involved in the functioning of an enzyme (as a cofactor) or metal activators. They are eight in number- Fe, Zn, Mn, B, Cu, Mo, Cl, and Ni.
Essential Mineral Elements Table at a Glance
| Elements | Functions | Deficiency symptoms |
|---|---|---|
| C,H,O | Structural framework, protoplasmic constituents, H+ governs pH, oxygen is the terminal electron acceptor in respiration, storage of food etc. | Normal growth cannot occur as they are building blocks of the body. |
| Nitrogen (N) | Required for the synthesis of amino acids, proteins, nucleic acids, vitamins, hormones, coenzymes, and chlorophyll. | Stunted growth, late lowering, chlorosis that appears first in older leaves, premature leaf fall, etc. |
| Phosphorus (P) | Required for the synthesis of nucleic acids, phospholipids, ATP, NAD and NADP. Constituent of the cell membrane and some proteins. | Poor growth, especially of roots. Leaves appear dull green. Often leads to premature leaf fall and delayed flowering. |
| Potassium (K) | Activates about forty enzymes. Associated with K+/Na+ pump in active transport, anion-cation balance in the cells. Brings about the opening and closing of stomata. Common in cell sap in plant vacuoles and helps in turgidity of cells. | Stunted growth. Yellow and shrivelled leaf margins. Mottled interveinal chlorosis appearing first in older leaves and premature death. |
| Calcium (Ca) | Present as calcium pectate in the middle lamella of the cell wall that joins adjoining cells together. Activates enzymes needed for the growth of root and shoot tip. Required for cell division, cell enlargement and translocation of carbohydrates. | Chlorosis of young leaves, degeneration of meristems, chlorosis, necrosis and curling of leaves. |
| Magnesium (Mg) | Forms part of the chlorophyll molecule. Activates enzymes of phosphate metabolism. Important for fats and carbohydrates metabolism. Essential for binding components of ribosomes. | Interveinal chlorosis with purple anthocyanin pigmentation, especially of older leaves, chlorotic areas may turn necrotic, reduced growth, etc. |
| Sulphur (S) | As a constituent of amino acids- cysteine and methionine and hence some of the proteins. Present in coenzyme A, vitamins (thiamine and biotin.) increases root development. Increases the nodule formation in legumes. | Chlorosis like in nitrogen-deficient plants, stunted growth, leaf curl, less juice content in citrus fruits, reduced nodulation in legumes, etc. |
| Iron (Fe) | Needed for the synthesis of chloroplast protein and so affects the chlorophyll and carotenoid synthesis. As a constituent of ferredoxin and cytochromes. Activates the enzyme catalase. | Interveinal chlorosis, particularly in young leaves. May be localized to a single leaf or branch due to limited mobility. |
| Manganese (Mn) | Activates enzymes of respiration, photosynthesis and nitrogen metabolism. Component of oxygen-evolving complex. Involved in oxidation-reduction and decarboxylation reactions during respiration. | Leaf – flecking or grey spots due to chlorosis and necrosis in interveinal zones. Causes grey speck of oat, marsh spot disease of a pea. |
| Molybdenum (Mo) | Required for nitrogen fixation. Activates the enzyme nitrate reductase. | Mottled chlorosis with marginal necrosis in leaves. May lead to abscission of flowers. Causes whiptail of cauliflower. |
| Boron (B) | Increases the uptake of calcium. Essential for meristem activity and growth of pollen tube. Involved in translocation of carbohydrates. Involved in the synthesis of proteins, pectins and nucleic acids. | Death of stem and root apices, loss of apical dominance, rosetting of leaves, stem brittle but stout. Reduced flower production. Causes heart rot of beets, the brown heart of turnip, etc. |
| Copper (Cu) | Component of oxidase enzymes, plastocyanin, RuBP carboxylase, etc. involved in electron transport in photosynthesis. | Reduced absorption of Co2. Causes dieback of shoots. Necrosis at the tip of young leaves and then the margins. Skin splitting or exanthema in citrus. |
| Zinc (Zn) | Component of indol-acetic acid (IAA) – a plant growth substance. Activates dehydrogenases and carboxylases. Present in enzyme carbonic anhydrase. | Little leaf and mottle leaf condition. Reduction in internode length. Rosette type growth. Causes whip tip of maize, khaira disease of rice, sickle leaf of cocoa. |
| Chlorine (Cl) | Essential for O2 evolution in photosynthesis as it is a component of the oxygen-evolving complex. Anion-cation balance in cells. | Bronze. Colour in leaves. Chlorosis, necrosis, swollen root tips. Flower abscission. |
| Nickel (Ni) | Metabolism of urea and ureides. | Leaf tip necrosis. |
